Embodiments of the invention relate generally to electric machine rotor bars and, more particularly, to a bi-metallic electric machine rotor bar.
Often, rotor bars of an electric machine such as an electric motor or generator are manufactured of one material. For example, rotor bars are often made of aluminum because of its electrical properties and the costs associated with “working” aluminum.
It has been found that the running efficiency of an electric machine can often be increased by decreasing the electrical resistance of the respective rotor bars. In other words, an electric machine having rotor bars with lower electrical resistance tends to operate more efficiently than a comparable electric machine having rotor bars with a higher electrical resistance (i.e., as rotor bar resistance decreases the electric machine running efficiency often increases).
To exploit this relationship between rotor bar resistance and running efficiency, rotor bars have been manufactured from materials having a lower electrical resistance than aluminum. For example, rotors bars made up of copper have been manufactured. However, due to the high melting point of copper, as compared to aluminum, and the difficulties associated with working with copper, copper rotor bars tend to be more costly than aluminum rotor bars.
It would therefore be desirable to provide an apparatus and method for cost effective manufacture of rotor bars that positively affect the running efficiency of an electric machine.